AC103A8D public key ?

Hi,

I am trying to check ilmbase download:

$ wget http://download.savannah.gnu.org/releases/openexr/ilmbase-2.2.0.tar.gz
$ wget http://download.savannah.gnu.org/releases/openexr/ilmbase-2.2.0.tar.gz.sig
$ gpg --verify ilmbase-2.2.0.tar.gz.sig
gpg: assuming signed data in `ilmbase-2.2.0.tar.gz'
gpg: Signature made Sun 10 Aug 2014 07:11:49 AM CEST using RSA key ID AC103A8D
gpg: Can't check signature: public key not found

Where is the public key AC103A8D ? I could not find it anywhere :

$ gpg --keyserver pgp.mit.edu --search-keys AC103A8D
gpg: searching for "AC103A8D" from hkp server pgp.mit.edu
gpg: key "AC103A8D" not found on keyserver


Thanks much